Levels 3, 4, 5
Levels 3, 4, 5 are all designed to constantly sense the surrounding environment and automatically adjust a range of features (including noise reduction, directional focus, speech enhancement, automatic volume, impact noise reduction, whistle reduction etc) to optimise both speech intelligibility and comfort in noise.
Importantly, these devices all feature ear-to-ear binaural synchronisation – meaning that the devices work together such that the automatic adjustments made in each are dependent on the input at the other ear. This vastly improves the devices’ ability to reduce noise – for example by reducing the volume of the device facing noise (ie a car window) whilst retaining the volume in the ear facing the speaker.
The differences between level 3, 4 & 5 correspond to the range of environments the devices can automatically sense and the degree and speed with which they can adjust.